THURSDAY, Sept. 5 (HealthDay News) -- Eating a Mediterranean diet may be good for your brain and might reduce the risk of dementia, a new review suggests.

A Mediterranean diet includes higher amounts of olive oil, vegetables, fruit and fish. Higher adherence to the diet involves more consumption of fruit and vegetables and fish, and less consumption of meat and dairy products.

Researchers analyzed data from 11 observational studies and one randomized controlled trial. Nine studies found that people with higher adherence to a Mediterranean diet had better brain function, lower rates of mental decline and a reduced risk of Alzheimer's disease.

However, close adherence to a Mediterranean diet had an inconsistent effect on mild cognitive impairment, according to the article in the current issue of the journal Epidemiology.

Many studies have linked a Mediterranean diet to a lower risk of age-related diseases such as dementia, but this is the first systematic review of such research, according to the British researchers at the University of Exeter and colleagues.

"Mediterranean food is both delicious and nutritious, and our systematic review shows it may help to protect the aging brain by reducing the risk of dementia. While the link between adherence to a Mediterranean diet and dementia risk is not new, ours is the first study to systematically analyze all existing evidence," review leader Iliana Lourida said in a university news release.

While the new research uncovered a link between the Mediterranean diet and brain health, it didn't prove a cause-and-effect relationship.

Lourida is with the U.K's National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care in the South West Pensinsula.

"Our review also highlights inconsistencies in the literature and the need for further research. In particular, research is needed to clarify the association with mild cognitive impairment and vascular dementia," she said. "It is also important to note that while observational studies provide suggestive evidence, we now need randomized controlled trials to confirm whether or not adherence to a Mediterranean diet protects against dementia."